The molecular basis for the proposed cariogenic properties of Actinomyces viscosus will be investigated in this proposal. The specific attachment of the organism to cemental surfaces and epithelial cells will be examined utilizing in vitro assay systems. The role of levans, extracellular slime or other macromolecules in the specific adherence mechanisms will be examined primarily by utilizing mutants of A. viscosus defective in synthesizing individual polysaccharide molecules. This approach will also be utilized to determine the role of these polysaccharides in the specific aggregation of A. viscosus to Veillonella alcalescens. The glucan binding protein of A. viscosus will be characterized following purification on glucan-affinity columns. The role of plasmids in glucan binding will be assessed by determining the presence or absence of these elements in spontaneous or induced non-glucan binding variants. The molecular basis for levan metabolism by A. viscosus will also be determined. The enzymes involved in levan metabolism will be characterized and the mode of regulation of these enzymes determined.